This invention relates generally to improvements in and relating to valve assemblies, for stopping, regulating and opening fluid passage in the valve. The kind of fluid may be gas, steam or liquid. However, the liquid is best for being handled by the valve assembly according to the present invention.
Conventional valve cocks, or more preferably cocks have a cone-shaped cock proper as its valve member. The cock proper has a lateral fluid passage opening therethrough for allowing, regulating or stopping fluid flow therethrough, depending upon the selected position of the cock proper relative to valve seats formed in the cock body housing the cock proper. For control of the fluid flow, the cock proper is rotated around its axis as desired.
On account of rotational manipulation of the cock proper, effective seal can not always be assured so that fluid leakages may occur rather frequently.
In order to obtain effective seal between the cock proper and its mating seats, strong thrust must be applied to the cock proper, thereby the latter is held in rather high pressure contact with the seats. This fact may frequently lead to mechanical and mostly localized damages of the seat surfaces.
As an advantage of this kind of valves, however, substantially undisturbed fluid passage can be established when the cock is manipulated to its full-open position.
As another kind of valve assembly somewhat similar to the objects of the present invention, conventional gate valves may be referred to. This kind of valve has a slidable gate as its valve member movable perpendicularly to the fluid passage which is formed laterally through the valve body. It should be mentioned, however, that each of the two valve-seating areas is rather small on account of its arrangement on an ideal plane which is in coincidence with the wedging operating surface of the gate. In this case, however, localized stress concentration, wear an fluid leakage can not be avoided on the valve seat surface during extending service and frequent on-off operations of the valve.
Therefore, the main object of the present invention is to provide an improved valve assembly representing an idealized combination of the gate valve and the valve cock in its essence, providing thereby a substantially broaded valve seat area, a smoother fluid passage and a lighter on-off control possibility.
For this purpose, the invention proposes such an improved valve assembly comprising a valve body unit having a fluid passage laterally arranged therethrough; a non-rotatably valve member movable within the valve body perpendicular to said fluid passage and holdable at any position at and between a full-closing position and a full-opening position relative to said fluid passage; said valve member taking a shape close to a true cylinder and having a taper of 1/30-1/10; and a valve-operating mechanism mounted rotatably in said valve body and kept in thread engagement with said valve member.
The valve body and the valve member are made of hard synthetic resin. It has been found that a better and smoother valve-operating possibility is obtained when the material of the valve member is softer than that of the valve body.
In this respect, PVC and PVDF are highly recommendable for the valve body, while polypropylene resin is highly recommendable for the valve member.
A pair of circularly closed and opposedly arranged ridge projections are cast on the outer surface of the valve member in such a way that these are brought into a sealing engagement with the valve seats when the valve member has been brought into its closing position.
There is provided a shallow concave recess formed in the bottom wall surface of said valve member and kept in fluid connection with the axial bore of the latter adapted for avoiding fluid trapping which may otherwise occur when said valve member is being brought into its closing position.
The valve member is connected with the valve gear through threaded connection via a valve spindle or stem, the latter being comprised of a resin sheath element and a metal core shaft, so as to increase the rigidity of the valve spindle.
The said valve member may be formed with a pair of radially opposite projections which are kept in slidable engagement with a pair of parallel guide grooves arranged in the interior of said valve unit and perpendicular to said fluid passage.
The valve member may be made hollow for providing an idle space adapted for allowing trapped fluid which is present at the last stage of a valve closing operation, to escape thereinto, thus making the valve-closing action lighter than otherwise.
The working end of the valve member may be made preferably and generally concave, so as to allow the treating fluid flow in an undisturbed manner when the valve member is positioned at its full-open position.
Each of valve seats practically and partially defining a fluid inlet opening and a fluid outlet opening arranged in line in the valve body, takes the form of a circular ring developed on as only slightly coned surface close to that of a true cylinder which surface is taken by operating part of the valve member. In this way, the valve seat surface may be substantially broadened in comparison with that of the correspondingly sized gate valve.
If both the valve member and the valve body are made of metal, the precise grind-in operation must be employed for the realization of an optimum seating effect in the fluid stop and sealing position of the valve assembly. This will cause naturally an uneconomical production efficiency. At the same time, such an inconvenience that the valve operating torque will become substantially high is met. When, for avoiding this disadvantageous effect by selecting proper plastics for the both main valve constituents, the valve body will become bulged out under the influence of the operating fluid pressure. This will cause to invite a fluid leak gap between the valve member and the seat.
This ill effect will become higher, when the fluid has elevated temperatures.
A second object of the invention is thus to provide an improved valve assembly adapted for suppressing the above disadvantage.
These and further objects, features and advantages of the invention will become more apparent when read the following detailed description of substantially a preferred embodiment of the invention with reference to the accompanying drawings in which